1. Field
Embodiments relate to an image forming apparatus, a control method for the same, and a motor state detector, which serve to detect out-of-step of a motor.
2. Description of the Related Art
A motor is an electric device that generates rotation power using electric energy. Among various shapes and kinds of motors, stepper motors are classified into a constant-voltage type and a constant-current type according to an excitation current control method.
A constant-current type stepper motor is based on current control, in which current applied to a motor coil is detected via a resistor and a switching device to control supply of current is subjected to pulse width modulation control with a constant frequency or constant off-time based on the detected current, whereby the amount of current supplied to the stepper motor may be kept constant.
Although the stepper motor, which is rotated by a predetermined angle according to an input frequency, performs accurate rotation, and therefore does not need feedback for detection of a motor position (revolutions per minute or rotation angle), an encoder to verify the operating state of the stepper motor may be necessary. The encoder, which serves to verify rotation of the stepper motor, may additionally need a slotted rotating disc installed to a rotating shaft of the stepper motor, and moreover a light-emitting element and a light-receiving element may be added to transmit light through a slot of the rotating disc and to receive the transmitted light.
The encoder may increase the price of the stepper motor and the size of the entire stepper motor, and the resulting stepper motor is susceptible to restrictions as to an installation space thereof (that is, a need for a wider space is present).
Further, the encoder type may be impossible to detect when the stepper motor begins to abnormal operate, and therefore may be unable to predict and prevent out-of-step of the stepper motor.
Furthermore, when the stepper motor unintentionally stops, it may be difficult to judge whether the stepper motor stops due to out-of-step, due to an increased device load, or due to control software error.